This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPP third generation partnership project
ACK acknowledgment
CN core network
CSG closed subscriber group
eNB evolved NodeB, EUTRAN network access node
EPC evolved packet core
EUTRAN evolved UTRAN (LTE)
GW gateway
HeNB home eNB
HNB home NodeB
HO handover
ID identity
IMSI international mobile subscriber identity
LTE long term evolution (EUTRAN)
MAC medium access control
MM/MME mobility management/mobility management entity
NB NodeB, UTRAN network access node
RAN radio access network
RANAP radio access network application part
RRC radio resource control
S-GW serving gateway
SRNS serving radio network subsystem
UE user equipment
UMTS universal mobile telecommunication system
UTRAN universal terrestrial radio access network
Both the UTRAN/UMTS and the EUTRAN/LTE system include deployments of what are generically termed femto nodes. In UTRAN (3G) these are termed HNBs and in LTE (4G) these are termed HeNBs. Apart from possibly allowing emergency calls, typically these femto nodes offer wireless voice and data service to only certain authorized UEs which are the members or subscribers, referred to as the node's/cell's CSG. More generally the femto nodes privilege their subscribers and authorized guests for some wireless service as compared to non-subscribers. Some femto cells are arranged contiguously as a group such as across a university or corporate campus that serves a single subscriber list, and so femto networks are referred to as CSG networks whether or not they operate solo or as part of such a group. UE's also have stored in their local memory a CSG list which identifies all those CSG networks to which the UE is authorized access.
In UTRAN it is mandatory that there is a HNB GW supporting the femto deployments; this HNB lies functionally between the CN and the HNBs. In LTE the HeNBs may be connected to a HeNB GW similar to UTRAN or they may be directly connected to CN. FIG. 1 illustrates an LTE deployment with a HeNB GW, in which the CN is represented as the MME/S-GW. The 3G arrangement is similar but with the 3G network controller in place of the MME/S-GW.
While femto nodes are often characterized as restricting access to non-subscribers, in fact they can operate in other modes besides that closed access mode. In the hybrid access mode the HNB/HeNB operates as a CSG cell where at the same time non-CSG members are allowed access, and in the open access mode the HNB/HeNB operates as a normal cell (i.e. a non-CSG cell). Additionally, in 3G there is the possibility of having non-CSG capable UEs, namely legacy UEs which do not have the capability to support certain CSG-specific functionalities. The 3G system currently allows access control for such UEs in cell access or mobility scenarios at the HNB GW, but this is the exception to typical practice and in the description below it is assumed that the described UE is CSG-capable.
Current mobility scenarios involving CSG-capable UEs and LTE HeNBs or 3G HNBs are based on the assumption that the core network will perform access control aimed at verifying whether the UE is a member of the CSG supported by the target cell. The results of such access control can be the success or failure of the mobility procedure when a UE is moving towards CSG closed cells, and in a less severe case can result in improperly prioritizing or de-prioritizing a UE in a target cell for the case the UE is moving toward hybrid cells.
Consider the two mobility scenarios shown at FIG. 1, which reflect the LTE system but are equally valid for the UTRAN system also. In a first case the UE is moving from HeNB#1 to HeNB#2 both served by the same HeNB GW and the mobility signaling messages flow is shown as intra GW mobility signaling. In a second case the UE is moving from HeNB#2 served by the HeNB GW to (macro) eNB#1 served by a MME/S-GW and the mobility signaling messages flow is shown as inter GW mobility signaling. In each of these for both LTE and UTRAN access control will not be possible because the mobility signaling messages do not cross any node which has possession of the subscriber information for the UE, which would allow for access control to be carried out.
The UE's subscription information is termed an “Allowed CSG List”, which conventionally is passed to the HNB GW in cases when the UE is paged within the home cell. Therefore if the HNB/HeNB GW could obtain the UE's allowed CSG list via paging, access control would be possible whenever the UE sets up signaling connections in response to being paged. The problem with this extension is that there is no mechanism to ensure that this information is sent to the HNB/HeNB GW for the case in which paging has not occurred in the cell but the UE needs to be involved in an enhanced mobility procedure for one of the scenarios shown at FIG. 1. Additionally there is no mechanism to update UE's allowed CSG list at the HNB/HeNB GW once it changes.
In scenarios where the HNB/HeNB itself carries out access control during the mobility scenarios shown in FIG. 1, the HNB/HeNB should have the CSG-Subscription status of UE in the possible target cells for which mobility is possible. The relevant information in the UE's allowed CSG list needs to be communicated to the serving cell and to the potential target cells where such cells are an HNB/HeNB cell in order to allow for access control.
Document R3-091552 by CATT entitled “Access control for inbound handover” (3GPP TSG-RAN WG3 #65; Shenzen, China; 24-28 Aug. 2009) suggests including the allowed CSG list in the UE CONTEXT SETUP REQUEST message for the purpose of allowing the serving eNB to perform access control instead of the CN while the handover procedures were still carried out via the CN. Similarly this document also mentions including the allowed CSG List in the HANDOVER REQUIRED message to allow the HNB GW to carry out access control when the mobility procedures are still carried out via the CN.
As stated at page 1 of document R3-091552, the problem it addresses is how to perform access control for macro to femto mobility procedures via the core network, which is a different from the mobility shown at FIG. 1. For this reason document R3-091552 gives no reason to include the allowed CSG list in any other messages since it always foresees core network involvement during a UE relocation. Moreover, document R3-091552 entails informing the complete CSG-List of the UE.
The exemplary embodiments detailed below are directed to a different purpose, the exchange of the CSG subscription information needed for the nodes such as the HNB/HeNB GW or the HNB/HeNB for the purpose of permitting mobility procedures to avoid routing via the core network. Certain exemplary embodiments further support mobility scenarios which utilize soft-handoffs, where the radio resources for the UE being handed over are allocated to the target access node (HNB/HeNB) based on the UE's CSG subscription.